Validation of lactate and glucose in cerebrospinal fluid (CSF) on a Radiometer blood gas analyzer ABL90 Flex plus.

Purpose: Rapid determination of cerebrospinal fluid. (CSF) glucose and lactate is required by emergency rooms and intensive care units. Long turnaround time (TAT) on test results negatively impacts timely diagnosis and treatment of neurological infections like meningitis.

Methods: The CSF glucose and lactate assays were evaluated on a blood gas analyzer, Radiometer ABL90 Flex Plus. Linearity, limit of quantitation (LOQ), and precision were determined using fresh and spiked patient CSF samples. Fifty-four fresh and 49 frozen CSF samples were used to compare the method againstAbbottArchitectC16000. An inter-laboratory comparison was done across eight hospital sites having ABL90 Flex Plus. The stability of both tests was tested for 48 h at ambient and refrigerated temperatures. Results were compared between centrifuged and uncentrifuged fresh CSF samples to determine if particulate in uncentrifuged samples impacted analysis.

Results: Glucose and lactate assays were linear over a broad analytical range of 1-45 mmol/L and 0-37 mmol/L, respectively, and demonstrated a good correlation with the routine chemistry laboratory method. LOQ was determined as 0.4 mmol/L for CSF glucose with a coefficient of variation (CV) of 14.7 % and 0.2 mmol/L with 0 % CV for CSF lactate respectively. Repeatability and reproducibility show small imprecision for both these assays. Glucose and lactate were stable for over 48 h at room or refrigeration temperatures. Sample particulates had no impact on the measurement. The inter-laboratory comparison was within total allowable error for glucose and lactate.

Conclusions: Acceptable performance characteristics, small sample volume, and rapid TAT make ABL90 Flex Plus an acceptable alternative analyzer for CSF lactate and glucose.